There’s a lot of information out there about sunscreen safety, and not all of it is reliable. We asked a top expert, Elizabeth Buzney, MD, outpatient clinical director of the Department of Dermatology at Brigham and Women’s Hospital and assistant professor of dermatology at Harvard Medical School, to address some common questions about sunscreens. She also serves on The Skin Cancer Foundation’s Photobiology Committee.
Q: As a dermatologist and photobiologist, you’re an expert on the effects of sunlight on skin as well as sun protection and how it works. When some people say they’re concerned about the safety of sunscreens, how can we put that into perspective?
Dr. Buzney: For starters, we know that the sun causes most skin cancers. That is absolutely proven. We also know that in some cases, skin cancer can be deadly. We can talk about the alleged risks of sunscreens all you want, but the truth is that they help protect you from the potentially deadly risks from the sun.
We have also proven that sunscreen helps prevent skin cancer. Two important Australian studies showed that melanoma was reduced by 50 percent and squamous cell carcinoma by 40 percent in those who used sunscreen daily. That’s huge. So keep slathering on the sunscreen!
That said, I want to stress that when you think about sun protection, sunscreen is important, but you should also think beyond sunscreen. The safest and most effective method, used throughout history, is to minimize your exposure to the sun and wear clothing and hats. Any discussion of sun protection has to start with those.
Q: How do you respond when people say they worry about chemicals in their sunscreen?
Dr. Buzney: They may not think about it this way, but all sunscreen ingredients are chemicals. A molecule is a chemical. Even the “physical” sunscreens containing zinc and titanium are chemicals. Of course, there are different kinds of chemicals, and they can act in different ways. A more accurate classification system for sunscreen ingredients would be “organic” and “inorganic.” Organic ingredients are carbon-based molecules, such as avobenzone and oxybenzone. Inorganic ingredients are the minerals zinc oxide and titanium dioxide.
Q: Which types of sunscreen are least likely to cause skin sensitivity?
Dr. Buzney: When you think about allergy or sensitivity to a sunscreen, don’t assume it’s because of the active ingredient. A true allergy to the active ingredients is quite rare. It’s far more common to experience sensitivity to the inactive ingredients in sunscreens. There are emulsifiers, preservatives, fragrances, plant extracts, antioxidants and other ingredients that can cause contact dermatitis, including “natural” ingredients. For example, poison ivy is natural!
Some products have many inactive ingredients, and it can be difficult to identify which one is causing the trouble. An allergic reaction typically takes three to five days to develop. I often counsel my patients who have a sunscreen sensitivity to use the inorganic sunscreens — those that contain zinc oxide and/or titanium dioxide, and with as few other ingredients as possible.
Q: Can you address the concerns some people have about certain ingredients in sunscreens?
Dr. Buzney: Attention has focused most on the ingredient oxybenzone and whether it is a hormone disruptor. One study showed uterine growth in rats. But if you look at that study, they fed the rats a huge amount of this chemical over the course of four days. To duplicate that amount in humans would take applying sunscreen all over the entire body every day for 70 years. It was not an accurate model for what a human would be exposed to.
We know that oxybenzone is absorbed into the body to some degree, and is excreted in urine and breast milk. We don’t know the implications of its use in women who are pregnant or breastfeeding, because that type of clinical study can’t be performed on this group. So, out of an abundance of caution, I suggest they use a zinc- or titanium-based sunscreen.
Other claims about sunscreen ingredients have been floating around on the internet but are not backed up by hard science. For example, you may have read that sunscreen containing vitamin A, or retinyl palmitate, can cause skin cancer, but there’s no data to support that. People who use those sunscreens, or any sunscreens, can still develop skin cancer, and the most likely cause is skin damage from sun exposure in earlier years. And protecting yourself now could prevent skin cancers in the future.